Such an image resolving detector may be a one-element, linear or matrix detector. With such a detector only a limited number of pixels corresponding to the number of the detector elements can be resolved. That applies in particular to infrared detectors which are provided with relatively few detector elements. If a large field of view is resolved by such a detector it is unavoidable that the spatial resolution suffers. There are applications, however, in which a relatively large field of view must be detected with high spatial resolution in order, for example, to identify a potential target in this field of view by means of image processing or to watch a plurality of non-contiguous field of view sectors.
To solve such problems it is known to divide the field of view into individual field of view sectors which are sequentially imaged on the detector. In a prior art solution this is achieved by suspending the detector together with an imaging optical system in a gimbal system and directing the optical system sequentially to the various field of view sectors. It is also known to deflect the path of rays by rotating diffracting or reflecting polygons or oscillating mirrors, thereby consecutively observing the field of view sectors.
Such an arrangement is expensive. The scanning rate is limited by the mechanics. The detector would permit a substantially higher scanning rate.
U.S. Pat. No. 5,448,395 discloses a device for observing a field of view by means of an image resolving detector, wherein an intermediate image of a field of view detected by the telescopic objective is generated. By means of a plurality of small lenses different portions of the intermediate image representing the various field of view sectors are imaged superimposed on the detector.